When comparing Genome2D vs GameMaker:Studio Marketplace, the Slant community recommends Genome2D for most people. In the question“What are the best 2D game engines?”Genome2D is ranked 56th while GameMaker:Studio Marketplace is ranked 63rd. The most important reason people chose Genome2D is:

It's the fastest gpu-based framework out there for flash. It's beautifully optimised. It has very low rendering latency, low level OpenGL calls that other tech simply cannot do (ie Unity) due to Stage3D, and thus can render a lot more data quicker

Ranked in these QuestionsQuestion Ranking

Pros

Pro

Lightning fast

It's the fastest gpu-based framework out there for flash. It's beautifully optimised. It has very low rendering latency, low level OpenGL calls that other tech simply cannot do (ie Unity) due to Stage3D, and thus can render a lot more data quicker

Pro

Cross-platform mobile, desktop and web

And with the HTML5 export, it also potentially supports development for the Wii U :)

Pro

Haxe!

Haxe is a strictly typed programming language that saves development time but still compiles high performance executables, and can build for tons of different platforms (flash, c++, html5, java, c#, etc.)

Pro

Access to direct draw features

Has access to direct draw features so you can make you own rendering structures (scene graphs etc).

Pro

Automatic dynamic batching

Pro

Component based architecture

Pro

Has a selection of free assetts

About 30 free assets are available.

Pro

Reasonably priced

Most assets are under $5. The more advanced assets can usually go for around $20-$25.

Cons

Con

Lacks documentation

The API documentation is minimal, there's not many tutorials and the ones that are there are very small and only cover the basics. If you want to learn how to properly use it, you have to ask the community or read the source code and figure it out.